<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>7_1_1-1-手动追踪变量的变化 -基本功能</title>
</head>

<body>


    <script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
    <script>
        //let 声明的变量只在 let 命令所在的代码块内有效。
        let a = 1;
        let b = 2;
        let sum = a + b;
        console.log(sum);
        a = 3;
        b = 4;
        console.log(sum);
    </script>
</body>

</html>